1. Technical Field
This invention relates to methods and apparatus for continuous measurement of motor symptoms in movement disorders. Specifically, it relates to methods and devices for continuous measurement of motor symptoms in movement disorders including Parkinson's disease and essential tremor by means of wearable kinematic sensors and signal processing analysis methods to determine impairment indices.
2. Related Art
Parkinson's disease (PD) is the second most common neurodegenerative disease and the most common serious movement disorder. It afflicts approximately 1 million in the US alone costing the economy over $25 billion annually. Levodopa is the most potent antiparkinson drug and is the primary therapy for most patients. However, continual use of levodopa over time causes fluctuations in bradykinesia (slowness of movement), tremor, and dyskinesia (uncoordinated writhing movements) and has variable effects on gait and posture. Accurate assessment of Parkinsonian motor impairments is crucial for optimizing therapy in clinical practice and for determining efficacy of new therapies in clinical trials. Subjective clinical rating scales such as the Unified Parkinson's Disease Rating Scale (UPDRS) are the most widely accepted standard for motor assessment. Objective static devices have also been developed to assess impairment more accurately and consistently. However, the value of both subjective and objective forms of static motor assessment may be limited in certain situations because each patient's motor state varies continuously throughout the day.
In recent years, large advances have been made in micro-electro-mechanical systems (MEMS) and inertial sensors, in particular. It is now possible to record body movements for hours with small, low-power, wearable sensors that include accelerometers, gyroscopes, goniometers, and magnetometers. However, the feasibility of using these sensors to quantify motor deficits associated with PD remains unknown.
Current inertial monitoring systems can be divided into three categories: computer-tethered, unit-tethered, and untethered. Computer-tethered devices connect the sensor directly to a computer. Unit-tethered systems connect the sensors to a central recording unit that is typically worn around the waist.
The only wireless untethered systems reported in the literature are “activity monitors,” which measure the coarse degree of activity at intervals of 1-60 s, typically with a wrist-worn device that contains a single-axis accelerometer. These devices are sometimes called actigraphs or actigraphers.
Most prior work on continuous monitoring of PD has used unit-tethered systems during in-patient studies. Most of these studies have used accelerometers, but some have used gyroscopes.
Currently there are no systems or detailed automatic methods designed to obtain impairment indices for Parkinson's disease or essential tremor in continuous monitoring settings in order to help guide therapy and or continuously monitor the symptoms of movement disorders.